(a) Field of the Invention
The present invention relates to a chemical mechanical polishing slurry composition which is used in the manufacture of semiconductor chips, and more particularly to a polishing slurry composition, which comprises a non-ionized, heat-activated nano-catalyst and is particularly useful for a process for chemical mechanical planarization of a metal layer, and to a polishing method using the same.
(b) Background of the Related Art
Semiconductor chips to which integrated circuit technology has been applied include numerous functional elements (devices), including transistors, capacitors, resistors and the like. Such individual functional elements are connected to each other by interconnects designed in specific shapes to form circuits. Integrated circuits have become smaller over time, and thus the function of one chip is also gradually increasing. In miniaturization of semiconductor chips, simply decreasing the size of devices has limitations, and thus studies on multilayer interconnect structures for forming each device in a multilayer structure have recently been actively conducted. To manufacture semiconductor devices having such multilayer interconnect structures, a process of planarizing metal layers by polishing must be carried out. However, because the metal layers are not easy to polish due to their high strength, in order to effectively polish the metal layer, the polishing process must be carried out after oxidizing the metal layers in the form of metal oxides having relatively low strength.
However, conventional chemical mechanical polishing slurry compositions have a shortcoming in that the efficiency of a chemical conversion process of oxidizing metal layers in the form of metal oxides is insufficient. Meanwhile, Korean Patent Registration No. 745447 discloses a method of promoting the oxidation of metal layers using a polishing slurry composition comprising hydrogen peroxide and iron salt (iron ion). However, because the disclosed method uses a large amount of iron salt, a metal layer being polished can be contaminated by iron ions, resulting in defects, or iron ions can remain on plugs (contacts between interconnects) to cause excessive oxidation, resulting in excessive etching. Thus, the choice of oxidizing agents and polishing particles, which can effectively oxidize a metal layer, to be polished, without causing defects on the metal layer, and the control of the concentration thereof are very critical to the development of chemical mechanical polishing (CMP) compositions.
Regarding catalysts and oxidizing agents, which are used in the chemical mechanical polishing processes, Korean Patent Laid-Open Publication No. 2001-0043798 discloses a metal oxide (e.g., TiO2) catalyst such as metal oxide (e.g., TiO2). However, the metal oxide (e.g., TiO2) catalyst is a photo-activated catalyst which has a problem in that it requires irradiation of light onto the catalyst between a substrate on which a CMP composition is applied and a pad for photo-activation of the catalyst. Moreover, Korean Patent Registration No. 10-736325 discloses a CMP composition in which an activating agent selected from the group consisting of metals known to be activated by Fenton oxidation are bound to the surface of particles and fluid. However, the CMP composition has a problem in that a metal layer being polished can be contaminated by the activating agent Fe ion, because the activating agent has a plurality of oxidation numbers even when the activating agent is not separated from the particles. Another problem is that an organic additive for reducing the contamination level is required.
In addition, U.S. Pat. No. 5,861,055 and Korean Patent Laid-Open Publication No. 2008-0070053 disclose chemical mechanical slurry compositions which comprise a metal silicide component as an abrasive, but recognize metal silicide as one of simple abrasives rather than an activating agent.